ARM: 6389/1: errata: incorrect hazard handling in the SCU may lead to data corruption

On the r2p0, r2p1 and r2p2 versions of the Cortex-A9, data corruption
can occur if a shared cache line is replaced on one CPU as another CPU
is accessing it.

This workaround sets two bits in the diagnostic register of the Cortex-A9,
reducing the linefill issuing capabilities of the processor and
avoiding the erroneous behaviour.

Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

2 files changed, 23 insertions, 0 deletions

diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index ab14c0a5d21e..0f89335b84c2 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -1063,6 +1063,20 @@ config ARM_ERRATA_742230
           instruction to behave as a DSB, ensuring the correct behaviour of
           the two writes.
 
+config ARM_ERRATA_742231
+        bool "ARM errata: Incorrect hazard handling in the SCU may lead to data corruption"
+        depends on CPU_V7 && SMP
+        help
+          This option enables the workaround for the 742231 Cortex-A9
+          (r2p0..r2p2) erratum. Under certain conditions, specific to the
+          Cortex-A9 MPCore micro-architecture, two CPUs working in SMP mode,
+          accessing some data located in the same cache line, may get corrupted
+          data due to bad handling of the address hazard when the line gets
+          replaced from one of the CPUs at the same time as another CPU is
+          accessing it. This workaround sets specific bits in the diagnostic
+          register of the Cortex-A9 which reduces the linefill issuing
+          capabilities of the processor.
+
 config PL310_ERRATA_588369
         bool "Clean & Invalidate maintenance operations do not invalidate clean lines"
         depends on CACHE_L2X0 && ARCH_OMAP4
diff --git a/arch/arm/mm/proc-v7.S b/arch/arm/mm/proc-v7.S
index 945f36341fa6..080129263eef 100644
--- a/arch/arm/mm/proc-v7.S
+++ b/arch/arm/mm/proc-v7.S
@@ -243,6 +243,15 @@ __v7_setup:
         orrle   r10, r10, #1 << 4               @ set bit #4
         mcrle   p15, 0, r10, c15, c0, 1         @ write diagnostic register
 #endif
+#ifdef CONFIG_ARM_ERRATA_742231
+        teq     r6, #0x20                       @ present in r2p0
+        teqne   r6, #0x21                       @ present in r2p1
+        teqne   r6, #0x22                       @ present in r2p2
+        mrceq   p15, 0, r10, c15, c0, 1         @ read diagnostic register
+        orreq   r10, r10, #1 << 12              @ set bit #12
+        orreq   r10, r10, #1 << 22              @ set bit #22
+        mcreq   p15, 0, r10, c15, c0, 1         @ write diagnostic register
+#endif
 
 3:      mov     r10, #0
 #ifdef HARVARD_CACHE